Playa Esqueleto and other outcrops - Braided, Conglomeratic
Submarine Channels: Upper Cretaceous
Kane, Ian1, Ben Kneller2,
Mason Dykstra3, William. D. McCaffrey1 (1)
In the area of Canyon San Vicente there
is excellent 3-D exposure of a submarine canyon, canyon-fill including mass
transport and channel-levee systems, with a submarine channel-levee system
eventually aggrading out of canyon confinement. Channel style varies stratigraphically from thick vertically amalgamated
channels to thin laterally accreting channels vertically segregated by
inter-channel/overbank facies.
Here we document the latter style and report facies
architectures from several channels of varying size. Channels are generally
incised into structureless sandstone, which may
represent frontal splays or channel mouth lobes, cutting down and ‘soling out'
at a level associated with older overbank deposits.
Channel bases are flat and marked by deposition of a thin sheet-like
conglomerate. Channel migration is marked by lateral accretion packages (LAPs) stacking towards the cut bank. The final stages of
channel fill are often by the deposits of sandy turbidity flows and debris
flows; overlying those and the LAPs is usually
another thin sheet-like conglomerate representing a final burst of the system.
After the final stages of channel fill and sheet conglomerate deposition there
is commonly deposition of laterally extensive debrites
possibly reflecting a lack of confinement. Thin bedded heterolithics
are found interbedded and are eventually succeeded by
another conglomeratic channel. All the evidence suggests active migration of
channels within a wider channel belt with flows (especially when unconfined)
interacting with topography related to the channel-belt margin (slumps and
slides) generating debris flows. We present a detailed facies
analysis and suggest methods for reservoir prediction.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California